Electrical machines are categorized into two..
Motor.
Generator.
There are two kinds of motor.
AC motor.
DC motor.
There are two kinds of three phase motor.
Synchronous motor.
Asynchronous motor.
The essential difference between asynchronous and synchronous engine , slip presents in asynchronous motor .At running condition slide of an asynchronous electric motor lies from 0 to at least one 1. . In asynchronous electric motor both starting and running torque is necessary. Asynchronous engine has moderate starting torque . Asynchronous motor is 
definitely a single fed motor.In asynchronous motor field is stationary armature rotates .
Three phase synchronous machines have a stationary three phase armature and a wound rotor. They are of two types:
synchronous generator or Alternator: Primary workhorse of the power generation 12v Motor industry; they are rotated mechanically by a prime mover at synchronous rate and it generates three phase electricity. Picture of PMA used in cars:
2. Synchronous motor: They are constant speed three phase machines capable of working at synchronous rate. They are mostly used in constant swiftness mechanical drives. They are more efficient compared to induction motors.
A synchronous machine has derived its name from the idea that the rotor will rotate in synchronicity with the rotating magnetic field.
In other words, for a 2 Pole machine (electric motor) the rotating magnetic field rotates at 3000 rpm; the rotor of synchronous machine also rotates at the same velocity i.electronic. 3000 rpm. This is achieved through special constructional features in production this types of devices. There is absolutely no slip in synchronous devices like regular induction motors.
Normally three phase supply is available commercially and the look is also designed for the same. That is why ‘three phase’ is certainly added with synchronous machine name.